416
Inorg. Chem. 1990, 29, 416-419
bond distance is 2.369 (3) A. There are no short intermolecular contacts between the molecules in the unit cell. Acbowl&ment. C.G.Y. and 1.P.M. thank the CTEC and the Australian Research Council for financial support. The X-ray structure was performed in the Molecular Structure Laboratory
of the University of Arizona. Supplementary Material Available: Tables of bond distances and angles, anisotropic thermal parameters, and calculated hydrogen atom wsitions (1 1 uages): a table of observed and calculated structure factors i21 pages). Ordering information is given on any current masthead page. 1
1
1
Contribution from the Department of Chemistry, University of South Carolina, Columbia, South Carolina 29208
Poly( pyrazolyl) borate Complexes of Terbium, Samarium, and Erbium. X-ray Crystal Structure of ([q3-HB(pz)3]2Sm(p-02CPh)),(pz = Pyrazolyl Ring) Daniel L. Reger,* Steven J. Knox, Jeffrey A. Lindeman, and Lukasz Lebioda Received July 19, 1989 The reaction of MCl, (M = Tb, Sm, Er) with 3 equiv of K[H2B(pz)2]yields [H(r-H)B(pz),],M. These complexes have properties similar to those of the yttrium analogue, which has been shown to have a trigonal-prismatic structure possessing weak agostic B-Ha-Y three-center interactions. The reaction of the metal halides with 2 equiv of K[HB(pz),] yields [HB(pz),12MCI,shown to be monomeric in solution for M = Sm. A similar reaction, which in addition contains 1 equiv of Na(02CCH3),yields [ [HB(pz),],M(02CCH3)J2.NMR spectra for all three types of these paramagnetic complexes are resolved for M = Sm and are was also prepared temperature dependent, showing these molecules are fluxional in solution. The complex { [HB(p~),l~Srn(0~CPh)}~ and the solid-state structure determined by X-ray diffraction: monoclinic, space group P2,/c, a = 13.264 (3) A, b = 35.821 (8) A, c = 15.544 (4) A, 0 = 115.06 ( 2 ) O , V = 6690 A', and Z = 4. The structure is an acetate-bridgeddimer in which the geometry about the samarium atoms fails to fit any regular polyhedron. Molecular weight studies show that this complex and {[HB( ~ z ) , ] ~ S ~ ( O ~ C Care H ,dimers ) ] ~ in benzene solution.
Introduction ( ~ z ) , ] ~ E ~ C I ( T Hwas F ) also briefly mentioned, but no experimental details were given.4a Takats has also recently published the We have recently been developing the chemistry of the early( M = Yb, Lu; /3-disynthesis of [HB(p~),]~M(@-diketonate) transition metals using poly(pyrazoly1)borate ligands. With ketonate = 2,2,6,6-tetramethyl-3,5-heptanedionate(dpm), 3tantalum and zirconium, a variety of stable complexes containing (trifluoroacety1)-d-camphorate).5 The Yb-heptanedione complex one tris(pyrazoly1)borate ligand, such as [RB(pz),]TaMe,CI (R = H, pz; pz = pyrazolyl ring),la [HB(3,5-Me2pz),]TaMe3Cl,Iawas characterized by X-ray crystallography and shown to have a square-antiprismatic solid-state geometry. The synthesis of [ R B ( ~ z ) ~ ] Z ~(R C I= , n-Bu, i-Pr),lb [HB(3,5-Me2pz),]Zr(O-t(M = Y, La, Ce, Pr, Nd, Sm, Eu, [ H B ( p ~ ) ~ ] ~ M ( a ccomplexes ac) Bu),,R3_, ( n = 1, 2; R = CI, Me, CH2Ph, C=CMe),lc and Tb, Dy, Ho, Yb, Lu; acac = acetylacetonate) has been reported [ HB(pz),]CpZrC12,1d have been prepared. It was not possible, by Jones and co-workers.6 X-ray crystallographic analysis dehowever, to prepare complexes containing two tris(pyrazoly1)borate termined that the cerium complex possesses a bicapped-trigoligands on tantalum or zirconium. Using the larger metals yttrium nal-prismatic geometry, while that of the ytterbium complex is and lanthanum, we have reported the following series of complexes derived from a square antiprism. With the exception of the containing two tris(pyrazoly1)borate ligands: [HB(pz),12YC1[q3-HB(pz)3]2[q2-HB(pz),lMcomplexes, all of these tris(pyra(H2OL [ H B ( P z ) , I ~ L ~ C ~ ( H Z[HB(pz)hYC1, O),~ [HB(pz),hYCI ( HPz) I 1HB(pz) 31 z Y ( P L - O ~ C C IH n , ~ and ) 1[HB(pz) ~ ~ Y ( P L - zoly1)borate complexes in both reports undergo dynamic rearrangements in solution. 02CCH3)2}2.2b[ HB(pz),] 2YC1(Hz0)2aand [HB(pz),] 2YCIWe report here the synthesis of complexes of the type [ H ( p ( have been structurally characterized by X-ray crystalH)B(pz)213M, [ H B ( P ~ ) ~ I ~ M andC ~~ [, H B ( P z ) ~ I ~ M ( O ~ C C H , ) ~ ~ lography and shown to have distorted-square-antiprismatic gefor the lanthanide metals samarium, terbium, and erbium. The , ) ~ also structurally ometry. { [H B ( ~ z ) , ] Y ( ~ - O , C C H ~ )was synthesis and solid-state structure of { [ H B ( ~ Z ) , ] ~ S ~ ( ~ - O ~ C P ~ ) } ~ characterized in the solid state and is an unusual example of is also reported. seven-coordinate yttrium.2b We have also described the synthesis and characterization of [H(~-H)B(PZ),],Y,~ a molecule that Experimental Section possesses three, three-center, bridging B-H.-Y interactions. In General Procedure. All operations were carried out under a nitrogen the solid state, the six nitrogen donor atoms form a trigonal prism atmosphere either by standard Schlenk techniques or in a Vacuum Atin which each rectangular face is capped by a B-H--Y agostic mospheres HE-493 drybox. All solvents were dried, degassed, and disbond. tilled prior to use. Infrared spectra were recorded on a Perkin-Elmer 78 1 In addition to our work, Takats has reported the synthesis of spectrometer. The 'H, IlB, and "C solution NMR spectra were recorded [q3-HB(pz)3]2[q2-HB(pz)3]Mcomplexes (M = Y, La, Ce, Pr, Sm, on a Bruker AM300 spectrometer using a 5-mm broad-band probe. An Gd, Er, Yb).4a The ytterbium derivative was characterized as IBM NR-80 spectrometer was also used to collect I3C NMR data. Proton chemical shifts are reported in ppm vs Me4Si. All carbon resoeight-coordinate as indicated by the above formula in solution4b nances are singlets with chemical shifts reported vs TMS by using the and in the solid state.& The solid-state structure was described solvents CD2CI2and CDCI, as internal standards (CD2C12resonance at as a bicapped trigonal prism. The synthesis of [HB53.85 ppm; CDCI, resonance at 77.00 ppm). Boron-11 chemical shifts are reported in ppm vs BF,.OEt,. Proton and "C variable-temperature NMR analyses were also performed on the Bruker AM300 NMR ( I ) (a) Reger, D. L.; Swift, C . A.; Lebioda, L. Inorg. Chem. 1984,23, 349. (b) Reger, D. L.; Tarquini, M. E. Inorg. Chem. 1982, 21, 840. (c) spectrometer at resonant frequencies of 300.13 and 75.47 MHz, reReger, D. L.; Tarquini, M. E. Inorg. Chem. 1983, 22, 1064. (d) Reger, spectively. The samples for variable-temperature studies were dissolved D. L.: Mahtab, R.: Baxter, J. C . ; Lebioda, L. Inorg. Chem. 1986, 25, in CD2CI2and then sealed in screw-capped 5-mm NMR tubes. Acti2046. vation parameters were calculated at the coalescence temperature.' (2) (a) Reger, D. L.; Lindeman, J. A.; Lebioda, L. Inorg. Chim. Acta 1987, 9
l39,71. (b) Reger, D. L.; Lindeman, J. A.; Lebioda, L. Inorg. Chem. 1988, 27, 3923. (3) Reger, D. L.; Lindeman, J. A.; Lebioda, L. Inorg. Chem. 1988, 27, 1890. (4) (a) Bagnall, K. W.; Tempest, A. C.; Takats, J.; Masino, A. P. Inorg. Nucl. Chem. Lett. 1976, 12, 5 5 5 . (b) Stainer, M. V. R.; Takats, J. Inorg. Chem. 1982. 21,4050. (c) Stainer, M. V. R.; Takats, J. J . Am. Chem. Soc. 1983, 105, 410.
0020-1 669/90/ 1329-0416$02.50/0
(5) Moffet, W. D.; Stainer, M. V. R.; Takats, J. Inorg. Chim. Acta 1987, 139, 75. (6) MOSS,M. A. J.; Jones, C. J.; Edwards, A. J. Polyhedron 1988, 7, 79. (7) Kegley, S. E.; Pinhas, A. R. Problems and Solutions in Organometallic Chemistry; University Science Books: Mill Valley, CA, 1986; pp 20-23.
0 1990 American Chemical Society
Poly(pyrazoly1)borate Complexes of Lanthanides UV-visible spectra were obtained in CH2CI2by using a Cary 210 spectrometer. Accurate mass spectra were run as solids on a VG 70SQ spectrometer; low-resolution spectra were run on a Finnigan 4521 GCmass spectrometer. Clusters assigned to specific ions show appropriate isotopic patterns as calculated for the atoms present. Elemental analyses were performed by Robertson Laboratory, Inc. K[HB(pz),] and K[H2B(pz),] were prepared by the published methodsag Anhydrous TbCI,, SmCI,, and ErCI, were purchased from Cerac/Pure Division and were used without further purification. Molecular weights were determined by freezing-point-depression measurements in an apparatus similar in basic design to that developed by S ~ h r i v e r . The ~ cell contains a Fenwal GB41P2 10K thermister, balanced against a Leeds & Northrup bridge circuit. A working calibration curve of ATverses molality was obtained by using known concentrations of doubly sublimed ferrocene. Data acquisition and processing were automated by interfacing the apparatus to a WYSE 286 computer. Typically, the mass of a sample was determined on a benchtop analytical balance and the sample then quickly transported into the drybox. The solute and the solvent were then introduced to the cryoscopy cell under the nitrogen atmosphere. Concentrations varied from approximately 5 to 30 g of solute/kg solvent. Triqdihydrobis(I-pyrazolyl)borato]terbium(III), [H(p-H)B(pz),],Tb (la). TbCI, (0.50 g, 1.9 mmol) and K [ H , B ( ~ z ) ~(1.05 ] g, 5.6 mmol) were placed in a 100-mL round-bottomed flask. T H F (70 mL) was added by syringe. The suspension was heated to reflux for 3 h, centrifuged, and filtered, and the solvent was evaporated under vacuum. The filtrate residue was extracted with toluene (40 mL) and filtered. Addition of hexane (30 mL) and cooling (ca. 0 "C) resulted in colorless crystals (0.28 g, 0.47 mmol, 25%). IR (Nujol mull, cm-I): 2455, 2440 (BH). UV-vis (A,, nm ,e(, M-l cm-I)): 349 (1.2), 351 (I.]), 355 (l.O), 363 (0.94), 366 (0.80), 371 (0.75), 482 (0.37). The mass spectrum shows the highest cluster for Mt - H at m / e 599. Anal. Calcd for C18H24N12B3Tb: C, 36.04; H, 4.04. Found: C. 35.75: H. 4.09. Bis[hydrotris( I-pyrazolyl)borato]chloroterbium(III), [HB(pz),],TbCI (24. TbCI, (0.50 g, 1.9 mmol) and K[HB(pz),] (0.95 g, 3.8 mmol) were placed in a 100-mL round-bottomed flask. T H F (50 mL) was added by syringe. The suspension was stirred at room temperature for 12 h, centrifuged, and filtered, and the solvent was evaporated under vacuum. The filtrate residue was extracted with benzene (40 mL), centrifuged, and filtered. The benzene was evaporated under vacuum to yield a white solid (0.72 g, 1.16 mmol, 62%). IR (Nujol mull, cm-I): 2456 (BH). The accurate mass spectrum shows clusters for Mt and Mt - CI. C18H20N1211B$5CITb,ClgH20N12"B2Tb:calcd m / e 620.1062, 585.1373; found m / e 620.1037, 585.1397. Bighydrotris( 1-pyrazolyl)borato]chloro(pyrazole)terbium(III), [HB(pz),],TbCI(Hpz). TbCI, (0.50 g, 1.9 mmol), K[HB(pz),] (0.95 g, 3.8 mmol), and Hpz (0.13 g, 1.9 mmol) were placed in a 100-mL roundbottomed flask. T H F (50 mL) was added by syringe. The suspension was stirred at room temperature for 6 h, centrifuged, and filtered, and the solvent was evaporated under vacuum. The filtrate residue was extracted with benzene (60 mL) and filtered. The benzene was evaporated under vacuum to yield a white solid (0.36 g, 0.52 mmol, 28%). IR (Nujol mull, cm-l): 3180 (NH); 2468 (BH). The mass spectrum shows Mt - HCI and Mt - HBpz clusters at m / e 651 and 619. Anal. Calcd for C2,H2,Nl,B2CITb: C, 36.69; H, 3.38. Found: C, 36.46; H, 3.58. (Acetato)bis[hydrotris(l-pyrazolyl)borato]terbium(III), [HB(pz),],Tb(O,CCH,) (34. TbCI, (0.30 g, 1.1 mmol), K[HB(pz),] (0.57 g, 2.3 mmol), and Na(02CCH,) (0.09 g, 1.1 mmol) were placed in a 100-mL round-bottomed flask. T H F (30 mL) was added by syringe. The suspension was stirred at room temperature for 8 h, and the solvent was evaporated under vacuum. Benzene (40 mL) was added by syringe, and the suspension was stirred at room temperature for 1 h and centrifuged. Filtration and evaporation of the benzene under vacuum yielded a white solid (0.68 g, 1.1 mmol, 94%). IR (Nujol mull, cm-I): 2450 (BH). The accurate mass spectrum shows a cluster for M+. C20H2,N120211B2Tb:calcd m / e 644.1 507; found m / e 644.1 503. Tris[dihydrobis( l-pyrazolyl)borato~manum(III),[H(p-H)B(pz),],Sm (lb). This complex was prepared in 23% yield as outlined above for la. lH N M R (CDCI,): 6 10.68, 6.82, 6.53 (s, s, s; pz), 4.05 (broad BH,). "C N M R (CD,CI,): ambient temperature, 6 143.42, 135.13 (3-C, 5-C (PZ)),105.08 (4-C (pz));-84 O C , 145.25, 137.15, 137.00 (3-C, 5-C (PZ)), 107.77, 107.62 (4-C (pz)). llB(lH}N M R (CDCI,): 6 -16.04. IR (Nujol mull, cm-I): 2455, 2440 (BH). UV-vis (A, nm (emax, M-I cm-I)): 346 (7.l), 362 (4.91, 379 (5.81, 405 (10.0), 480 (3.8). The accurate mass spectrum shows M t - H and M+ - BH4 clusters. C18H23N,21'B,152Sm, calcd m / e 592.1642, 580.1342; found m / e ClgH20N1211B2154~m: 592.1664, 580.1311. (8) Trofimenko, S. J . Am. Chem. Sot. 1967, 89, 3170. (9) Shriver, D. F.; Drezdzon, M. A. The Manipulation of Air-Sensitive Compounds, 2nd ed; Wiley: New York, 1986; p 38.
Inorganic Chemistry, Vol. 29, No. 3, 1990 417 Table I. Crystallographic Data for the Structural Analysis of l[HB(~z)slzsm(p-o,CPh)12 (4) formula: (C25H 5B2Nlz02Sm)2 fw = 1244.60 space group: P2,/c a = 13.264 (3) T = ambient b = 35.821 (8) 8, X = 0.71073 8, c = 15.544 (4) A pale = 1.385 g cm-, a = 90' p = 18 cm-I fi = 115.06 (2)' transm coeff = 1.174-0.793 y = 90' RF = 0.079 V = 6690 8,' RwF = 0.078 z = 4
ft
Bis[hydrotris( l-pyrazolyl)borato]chlorosaman~(~), [HB(pz),@SmCI (2b). This complex was prepared in 44% yield as outlined above for 2a. IH N M R (CDCI,): 6 8.61, 5.92, 4.47 (6, 6, 6; s, s, s; pz). 13C N M R (CDCI,): 6 141.40, 135.80 (3-C, 5-C (PZ)), 103.55 (4-C (PZ)). IlB N M R (CDCI,): 6 2.65 (d, J B H = 102 Hz, line narrowed). IR (Nujol mull, cm-I): 2480 (BH). UV-vis (Am, nm (ern, M-l cm-I)): 345 (7.0), 362 (4.8), 377 (3.7), 404 (9.8), 478 (2.1). The accurate mass spectrum shows Mt - H and Mt - CI clusters. ClsH19N12"B235C11s2Sm ClsH20N1211B2~s2Sm: calcd m / e 612.0925, 578.1314; found m/h 612.0936, 578.1317. (Acetato)bis[hydrotris(l-pyrazolyl)borato]samarium(III), [HB(pz),],Sm(O,CCH,) (3b). This complex was prepared in 93% yield as outlined above for 3a. 'H N M R (CDCI,): 6 8.31, 5.86 (s, s; two of the pz resonances, the third was not observed), 5.15 (broad CHI). I3C N M R (CD2CI2): 6 141.12, 135.83 (3-C, 5-C (Pz)), 103.75 (4-C (PZ)). IlB N M R (CDCI,): 6 1.23 (d, JaH = 68 Hz, line narrowed). IR (Nujol mull, cm-I): 2455 (BH), 1560 (CO,). The accurate mass spectrum shows clusters for M + - H and M t - 0 2 C C H , . C20H22N120210B"B152Sm, ClsH20N1210B11B152Sm: calcd m / e 635.1409, 577.1354; found m / e 635.1438, 577.1365. Anal. Calcd for C20H23N1202B2Sm:C, 37.80; H, 3.65. Found: C, 37.56; H, 3.58. Bis((1-benzoato)bis[hydrotris( I-pyrazolyl)borato]samarium(III)}, {[HB(pz)@n(p-OZCPh)),(4). This complex was prepared in 82% yield as outlined above for 3a, substituting Na(0,CPh) for Na(O2CCH,). IH N M R (CDCI,): 6 8.57,4.48 (broad, two of the pz resonances, the third was not observed), 5.89 (broad, C a s ) . IR (benzene, cm-I): 2457 (BH), 1520 (CO,). The mass spectrum shows clusters for M+, Mt - pz, and Mt - 02C(C6H5) at m / e 698, 632, and 578. Anal. Calcd for C25H25N1202B2Sm:C, 43.26; H, 3.92. Found: C, 43.02; H, 3.62. Tris[dibydrobis(l-pyrazolyl)boratojerbium(III), jH(p-H)B(p~)~l,Er (IC). This complex was prepared in 38% yield as outlined above for la. IR (Nujol mull, cm-l): 2455, 2440 (BH). UV-vis (A, nm e(,, M-' cm-I)): 381 (22.8), 489 (5.7), 525 (13.1), 654 (5.1). Anal. Calcd for CIgH24N12B3Er:C, 35.54; H, 3.99. Found: C, 35.49; H, 3.82. Bis[bydrotris( I-pyrazolyl) borato]chloroerbium( III), [HB(pz),],ErCI (2c). This complex was prepared in 48% yield as outlined above for 2a. nm (e-, M-l cm-I)): IR (Nujol mull, cm-I: 2455 (BH). UV-vis (A, 381 (13.31, 489 (6.21, 525 (7.6). 654 (4.6). The accurate mass suectrum shows M+ - H and M+ - C1 clusters. ClBH19N1210B"B35'C1166Er, C18H20N1210B11B166Er: calcd m / e 625.1070, 591.1459; found m / e 625.1073, 59 1.1465. (Acetato) bis[hydrotris( I-pyrazolyl)borato]erbium(III), [HB(pz),]?Er(02CCH,) (3c). This complex was prepared in 40% yield as outlined above for 3a. IR (Nujol mull, cm-I): 2455 (BH), 1575 (CO,). The accurate mass spectrum shows clusters for Mt - H and Mt - O,CCH,. C20H22N1202~oB11B~66Er, C1sH20N1210B11B166Er: calcd m / e 649.1514, 591.1459; found m / e 649.1520, 591.1444. Crystallographic Analysis of {[HB(pz),],Sm(p-O,CPh))z (4). A transparent prismatic crystal of 4 was mounted in a thin-walled capillary tube on a CAD-4 diffractometer. The unit cell was determined and refined from 25 general reflections. Crystal data, data collection parameters, and results of the analysis are listed in Table I. The length of one of the unit cell dimensions, b = 35.821 A, has forced us to use a small crystal and a relatively narrow scan range to avoid reflection overlap. This may have introduced some systematic errors due to which anisotropic refinement of the light atoms resulted in nonpositive definite tensors for a few atoms. We have therefore refined the structure by using a model in which thermal motion of the light atoms was isotropic. The aromatic rings were refined as rigid bodies. Our satisfaction with the structure stems from our primary interest being the degree of oligomerization of the molecule and the geometry about the samarium atoms. The structure was solved by the heavy-atom method and refined by using SHELX 76.1° Hydrogen atoms were placed in calculated positions and not (10) Sheldrick, G. M. "SHELX-76, Program for Crystal Structure
Determination"; Cambridge University Press: Cambridge, England, 1976.
418 Inorganic Chemistry, Vol. 29, No. 3, 1990
Reger et al.
Table 11. Fractional Atomic Coordinates with Esd's in Parentheses and Isotropic Temperature Factorsa XI. Ylb ZlC B, A2 xla Ylb Sm(l) 0.4328 (1) 0.1271 (0) 0.2098 11) 3.20 (2154) 0.4996 116) 0.1585 (4) 0.5297 (16j 0.1201 (4j 0.0436 (1 j 0.1608 ioj -0.0892 (1 j 3.72 0.5077 (16) 0.1050 (4) 0.2628 (14) 0.1471 (4) 0.2019 (11) 3.92 0.4640 (16) 0.1339 (4) 0.0757 (12) 4.42 0.1571 (5) 0.1080 (14) 0.2601 (12) 0.0449 (5) 0.1477 (7) 0.1614 (17) 3.40 0.1616 (21) 0.2521 (12) 0.0182 (5) 0.1378 (5) 0.1651 (IO) -0.0234 (15) 5.57 0.0229 (5) 0.3452 (12) 0.1274 (5) -0.0847 (15) 0.2154 (IO) 6.72 0.4108 (12) 0.0526 (5) -0.0299 (1 5) 0.1 174 (5) 0.3109 (10) 7.94 0.3582 (12) 0.0662 (5) 0.1 177 (5) 7.36 0.3561 (IO) 0.0861 (15) 0.0670 (8) 0.5219 (23) 6.20 0.1474 (15) 0.1280 (5) 0.3058 ( I O ) 0.0126 (13) 0.0760 (6) 3.81 0.2104 (IO) 0.0926 (15) 0.1381 (5) 0.0459 (6) -0.0620 (13) 4.20 0.0990 ( 5 ) 0.0709 (1 2) 0.3128 (14) 0.0523 (6) -0.1595 (13) 0.1803 (14) 0.1 136 (5) -0.0626 (1 2) 4.8 1 0.0864 (6) -0.1453 (13) 0.2453 (21) 0.0905 (7) -0.0095 (18) 3.96 0.1010 (6) -0.0390 (13) 0.1537 (15) 0.0424 (6) -0.1325 (13) 7.94 -0.2108 (16) 0.2027 (4) 0.1486 (15) 0.0059 (6) -0.1652 (13) 12.04 -0.3273 (16) 0.1975 (4) -0.1122 (13) 8.45 0.2302 (15) -0.0199 (6) 0.1608 (4) -0.3454 (16) 8.88 -0.0091 (6) -0.0265 (13) 0.3168 (15) -0.2401 (16) 0.1433 (4) 0.3219 (15) 0.0274 (6) 0.0062 (13) 5.83 -0.1569 (16) 0.1692 (4) -0.0468 (13) 4.00 0.2403 (15) 0.0532 (6) 0.1206 (5) -0.0128 (13) 0.1286 (13) 5.39 0.3289 (12) 0.2170 (5) -0.1006 (13) 0.1031 (5) 0.2508 (5) 0.0981 (13) 6.81 0.3593 (12) 0.0959 (5) -0.1885 (13) 0.1023 (13) 7.30 0.4676 (12) 0.2461 (5) -0.1551 (13) 0.1088 (5) 0.1354 (13) 4.85 0.5041 (12) 0.2094 (5) 0.1241 (5) -0.0465 (13) 0.4184 (12) 0.1914 (5) 0.1516 (13) 4.45 0.1072 (IO) -0.2186 (32) 0.0355 (14) 6.85 0.5306 (16) 0.1008 (4) 0.1985 (4) -0.1501 (14) -0.0115 (14) 6.21 0.1148 (4) 0.5941 (16) 0.2329 (4) -0.1780 (14) 0.0256 (14) 6.22 0.1508 (4) 0.6335 (16) 0.2593 (4) -0.0945 (14) 0.0955 (14) 4.87 0.1591 (4) 0.5944 (16) 0.2412 (4) -0.0150 (14) 0.1016 (14) 4.43 0.1282 (4) 0.5308 (16) 0.2036 (4) -0.0494 (14) 0.3959 (1 1) 0.1582 (5) 5.72 0.6935 (16) 0.0532 (16) 0.2391 (5) 0.4102 (11) 6.76 0.1797 (5) 0.7892 (16) 0.0668 (16) 0.2785 (5) 0.3216 (11) 6.38 0.1955 (5) 0.7734 (16) 0.2903 (5) 0.0829 (16) 0.1838 (5) 4.90 0.2525 (1 1) 0.6678 (16) 0.0793 (16) 0.2582 (5) 5.21 0.2984 (1 1) 0.1608 (5) 0.6184 (16) 0.0609 (16) 0.2266 (5) 0.1527 (21) 4.18 0.1921 (9) 0.61 15 (26) 0.2977 (16) 0.1803 (4) 0.2785 (11) 5.31 0.0729 (5) 0.6807 (15) 0.3508 (16) 0.2089 (4) 0.3551 (11) 6.74 0.0506 (5) 0.7537 (15) 0.2805 (16) 0.2407 (4) 0.0457 (5) 0.4196 (11) 5.10 0.7045 (15) 0.1840 (16) 0.2319 (4) 0.3828 (11) 3.81 0.0648 (5) 0.6010 (15) 0.1945 (4) 0.1946 (16) 0.2955 (11) 4.18 0.0817 (5) 0.5864 (15) 0.0895 (27) 0.2575 (IO) 0.4266 (14) 6.70 0.1670 (4) 0.4589 (16)
For samarium atoms, which were refined anisotropically,B values are given as E , = refined. Full-matrix least-squares refinements were carried out with + > 3 a ( 4 . Table
weights w = (c2(F) 0.0004p)-1 for reflections with I I1 shows atomic parameters for 4.
Results and Discussion Poly(pyrazoly1)borate complexes of terbium(", samarium(HI), and erbium(II1) are prepared by stoichiometric combination of the appropriate metal trichloride and ligand salts (eq 1-3). The MC13 + 3K[H,B(pz),] [H(M-H)B(Pz),],M + 3KCl (1)
-
MC13 2MC1,
+ 2K[HB(pz),]
1
4
[ H B ( P Z ) ~ ] ~ M+C I2KCl 2
+ 4K[HB(pz),] + 2Na(02CCH3)
-
( [ H B ( ~ Z ) ~ ] ~ M ( O , C C H+, )4KCI ~, 3
+ 2NaC1
(2)
(3)
M = Tb (a), Sm (b), Er (c) new complexes, 1-3, are freely soluble in THF, halocarbons, and aromatic hydrocarbons. They are somewhat stable in air, but complex 3 decomposes slowly and complex 2 decomposes rapidly in solution. A major decomposition product of 2 is [HB(pz)J2MC1(Hpz). This was verified by the direct preparation of this terbium complex by a reaction similar to that shown in eq 2 with the addition of 1 equiv of Hpz. The preparation and solid-state structure of the yttrium analogue has been reported The UV-visible absorption spectra of complexes 1 and 2 have been studied. The spectra for the complexes of each metal are superimpsable, and the spectra are not significantly different from
ZIC
0.5248 (14) 0.5371 (14j 0.4464 (14) 0.3782 (14) 0.2117 (9) 0.2759 (9) 0.3647 (9) 0.3554 (9) 0.2609 (9) 0.4281 (21) 0.0183 (12) 0.0065 (12) -0.0782 (12) -0.1186 (12) -0.0590 (12) -0.1202 (13) -0.1722 (13) -0.2102 (13) -0.1818 (13) -0.1262 (13) -0.3106 (13) -0.3884 (13) -0.3615 (13) -0.2670 (13) -0.2355 (13) -0.2029 (25) -0.3213 (13) -0.3713 (13) -0.3194 (13) -0.2374 (13) -0.2386 (13) 0.0570 (11) 0.0622 ( 1 1) -0.0183 (11) -0.0732 (1 1) -0.0267 (1 1) -0.1097 (14) -0.1386 (14) -0.1634 (14) -0.1498 (14) -0.1166 (14) -0.1637 (23)
B, A2 7.51 5.38 3.81 4.34 4.65 5.95 5.74 4.43 4.02 3.38 5.72 8.59 7.97 6.65 5.91 6.32 6.62 6.79 6.14 4.82 4.98 6.92 8.50 5.97 4.90 5.93 5.66 6.12 5.97 5.11 5.18 6.00 5.40 5.84 5.43 4.82 6.58 7.41 6.76 5.57 4.86 4.88
8/3A2~,~,uj,a*ja*,BiB/.
those observed for other Tb3+,Sm3+,or Er3+complexes." The 4f orbitals of the lanthanide elements are effectively shielded from ligand effects by the filled 5s and 5p orbitals. As a result, f-f transitions do not vary appreciably from complex to complex even with substantial changes in the type of ligand.12 Due to the paramagnetism of these complexes, meaningful NMR spectra could only be obtained for the samarium complexes. The samarium complex [H(p-H)B(pz),],Sm ( l b ) displays the same variable-temperature 13CN M R behavior as previously reported for the yttrium ~ o m p l e x .At ~ ambient temperature, three resonances are observed for the pyrazolyl ring carbon atoms, implying that all six rings of the three bis(pyrazoly1)borate ligands are equivalent. Lowering the temperature causes the resonances at 6 135.13 and 105.08 to broaden until at -66 "C both begin to split into two resonances. The resonance initially at 6 145.25 does not show any line broadening even at -84 "C. At this temperature the resonances at 6 135.13 and 105.08 are resolved into two equally intense resonances centered at 6 137.08 and 107.70 with separations of l l .2 and l l .4 Hz, respectively. The barrier to equilibrium as calculated from the resonance at b 135.13 at the coalescence temperature of -47 OC is 11.7 kcal/mol. This energy barrier is essentially equal to the barrier of 11.4 kcal/mol determined for [H(g-H)B(pz),],Y .3 Given this similarity in the N M R spectra of l b and the nearly superimposable IR spectra for all three type 1 complexes with that of [ H ( ~ - H ) B ( ~ z ) ~ ] ~ Y , (1 1 ) Spedding, F. H.; Daane, A. H. The Rare Earths; John Wiley and Sons, Inc.: New York, 1961; pp 17, 595. (12) Cotton, F. A,; Wilkinson, G.Advanced Inorganic Chemistry, 5th ed.; John Wiley and Sons: New York, 1988; Chapter 20.
Poly( pyrazolyl) borate Complexes of Lanthanides
Inorganic Chemistry, Vol. 29, No. 3, 1990 419
(A) and Bond Angles (deg) for { [ H B ( P z ) ~ ] ~ S ~ ( ~ - O ,with C P ~Estimated )J~ Standard Deviations in Parentheses Table 111. Selected Bond Distances
Bond Distances Sm(1)-O(1) Sm(1)-O(3) Sm(1)-N(12) Sm(l)-N(22) Sm(l)-N(32) Sm(l)-N(42) Sm(l)-N(52) Sm(l)-N(62)
O( l)-Sm(l)-O(3) O(l)-Sm(l)-N(l2) O( l)-Sm(l)-N(22) O(1)-Sm( l)-N(32) Figure 1. Numbered ORTEP drawing of { [ H B ( p ~ ) ~ ] ~ s r n ( p O ~ C(4). P h ) } ~ O( l)-Sm(l)-N(42) O(1)-Sm( 1)-N(52) Numbers for carbon atoms in many rings have been omitted for clarity. O( 1)-Sm( 1)-N(62) The numbering schemes for these rings are sequential as shown in the O(3)-Sm( 1)-N( 12) labeled rings. O(3)-Sm( 1)-N(22) it is reasonable to assume that these molecules all have the same O(3)-Sm( 1)-N(32) O(3)-Sm( 1)-N(42) trigonal-prismatic structure that includes the weak agostic B0(3)-Sm(l)-N(52) He-M three-center interactions. O(3)-Sm( I)-N(62) The samarium chloride complex 2b shows complex temperature-dependent N M R spectra similar to that of [ H B ( ~ z ) , ] , Y C ~ ~ ~ . N ( 12)-Sm( 1)-N(22) N ( 12)-Sm(l)-N(32) Repeated attempts to obtain crystallographic quality crystals of N ( 12)-Sm( 1)-N(42) any of these complexes have proven unsuccessful. Solution moN ( 12)-Sm( 1)-N(52) lecular weight studies ( I ,2-dibromcethane) with [HB(pz),l2SmC1 N(12)-Sm(l)-N(62) show that it is a monomer. This is an interesting contrast to N ( 22)-Sm( 1)-N( 32) [(C5Mes),YC1]z,13which is an unsymmetrical monochlorideN(22)-Sm( I)-N(42) N(22)-Sm( 1)-N(52) bridged dimer. This difference in structure is most reasonably N(22)-Sm( 1)-N(62) ascribed to the larger size14 of H B ( ~ z (cone ) ~ angle of 184') N(32)-Sm( 1)-N(42) compared to C5Me, (cone angle of 142'). N(32)-Sm( 1)-N(52) The acetate complex of samarium, 3b, also displays complex N(32)-Sm( 1)-N(62) temperature-dependent N M R spectra analogous to those of its N (42)-Sm( 1)-N (52) yttrium analogue.2b Crystals of these complexes did not prove N(42)-Sm( 1)-N(62) suitable for a solid-state structure. For this reason the phenylN(52)-Sm( 1)-N(62) acetate analogue, ([HB(pz)3]2Sm(p-02CPh)]2(4), has been 0(2)-Sm(2)-0(4) prepared and characterized in the solid state by X-ray crystal0(2)-Sm(2)-N(72) 0(2)-Sm(2)-N(82) lography. Freezing-point-depression measurements in benzene
show that ([HB(pz)3]zSm(p-02CPh)]zand {[HB(pz),l,Sm(~O,CMe)), are dimeric in solution. Molecular Structure of ( [ H B ( ~ Z ) ~ ] ~ S ~ ( ~ - O An ~ C ORTEP P~)],. drawing of 4 is shown in Figure 1; selected bond lengths and angles are shown in Table 111. The molecule is a dimer with the metals bridged by the acetate ligands. The samarium atoms, separated by 5.42 A, are eight-coordinate. Analysis of the geometry about samarium by interactive computer graphics indicates that none of the regular shapes such as a square antiprism, bicapped trigonal prism, or dodecahedron satisfactorily describe the geometry about either samarium atom. The closest analogue to the structure of 4 is [(~S-C5Hs)zYb(02CC6Fs)]2 (5), a molecule that is also dimeric.IS In both structures, the bridging carboxylate ligands are not symmetrical. Thus, the Sm-0-C angles in 4 within each bridging ligand differ by 13 and 19'. Another similarity is that the tris(pyrazoly1)borate ligands on each side of the dimer are staggered (taking the boron atom as the center of the ligand), similar to the cyclopentadienyl rings in 5. Conclusion A series of stable complexes with poly(pyrazoly1)borate ligands coordinated t o t h e metals y t t r i ~ m , s~a.m~ a r i u m , terbium, a n d
erbium have been prepared and characterized:
[H(pH)B-
(13) Evans, W. J.; Peterson, T.T.;Rausch, M. D.; Hunter, W. E.; Zhang, H.; Atwood, J. L. Organomerallics 1985, 4, 554.
(14) (a) Trofirnenko, S.; Calabrese, J. C.; Thompson, J. S . Inorg. Chem. 1987, 26, 1507. (b) Davies, C. E.; Gardiner, I. M.; Green, J. C.; Green,
M. L. H.; Hazel, N. J.; Grebenik, P. D.; Mtetwa, V. S. B.; Prout, K. J . Chem. Soc., Dalfon Trans. 1985, 669. ( I 5 ) Deacon,G. B.; Fallon, G. D.; MacKinnon, P. I.; Newnham, R. H.; Pain, G. N.; Tuong, T. D.; Wilkinson, D. L. J . Orpanomet. Chem. 1984,277, c21.
2.32 2.30 2.45 2.52 2.56 2.50 2.48 2.65
(1)
(2) (2) (2) (2) (2) (2) (2)
Sm(2)-O(2) Sm(2)-O(4) Sm(2)-N(72) Sm(2)-N(82) Sm(2)-N(92) Sm(2)-N(102) Sm(2)-N(112) Sm(2)-N(122)
2.34 2.38 2.54 2.49 2.45 2.62 2.52 2.52
Bond Angles 79.3-5) 0(2kSm(21-N(92) 76.6 (5) o ( ~ ~ - s & ~ - N ( I o ~ ) 136.3 (5) 0(2)-Sm(2)-N( 112) 125.1 (5) 0(2)-Sm(2)-N(122) 141.5 (5) 0(4)-Sm(2)-N(72) 75.5 (5) 0(4)-Sm(2)-N(82) 78.0 (4) 0(4)-Sm(2)-N(92) 98.6 (4) 0(4)-Sm(2)-N(102) 74.2 (4) 0(4)-Sm(2)-N(112) 146.8 (4) 0(4)-Sm(2)-N(122) 107.4 (4) N (7 2)-Sm( 2)-N (82) 140.5 (5) N ( 72)-Sm( 2)-N( 92) 74.0 (4) N(72)-Sm(2)-N(102) 73.8 (4) N(72)-Sm(2)-N( 112) 70.3 (4) N(72)-Sm(2)-N(122) 136.5 (4) N(82)-Sm(2)-N(92) 104.4 (4) N(82)-Sm(2)-N(102) 154.5 (3) N(82)-Sm(2)-N(112) 72.6 (4) N(82)-Sm(2)-N(122) 80.3 (4) N(92)-Sm(2)-N(102) 142.9 (5) N(92)-Sm(2)-N(I 12) 125.1 (4) N(92)-Sm(2)-N(122) 68.9 (5) N(102)-Sm(2)-N(112) 72.1 (5) N ( 102)-Sm(2)-N( 122) 128.5 (4) N(112)-Sm(2)-N(122) 76.6 (5) Sm( 1)-O( 1)-C( 131) 68.2 (4) Sm(2)-0(2)-C(131) 71.4 (4) O(l)-C(l31)-0(2) 82.6 (5) Sm(l)-0(3)-C(141) 74.6 (5) Sm(2)-0(4)-C(141) 96.8 (4) 0(3)-C(141)-0(4)
(2) (2) (2) (1) (2) (2) (2) (1)
142.6 (5) 145.4 j4j 72.5 (4) 105.3 (4) 74.1 (5) 141.8 (4) 79.5 (4) 127.4 (4) 131.1 (4) 76.6 (4) 69.0 (4) 68.9 (4) 125.5 (4) 133.9 (4) 150.5 (4) 78.3 ( 5 ) 70.6 (4) 83.7 (5) 138.5 (5) 68.3 (4) 141.8 (4) 102.1 (4) 74.1 (4) 71.3 (4) 70.7 (5) 150 (1) 163 (2) 124 (2) 168 (2) 149 (2) 121 (2)
(pz),l3M, tHB(pz)3l,MC1, [HB(Pz)312MC1(HPz) (M = y, T b and {[HB(pz)312Sm(ronly), I[HB(pz)3lzM(cL-OzCCH3))2 O,CPh)),. For the [H(p-H)B(pz),],M complexes, the M = Y complex has been characterized crystallographically3 and shown to have a trigonal-prismatic coordination of the nitrogen donor atoms with each rectangular face capped by an agostic B-H.0.Y interaction. The [ H B ( ~ Z ) ~ ] ~ Mcomplexes CI have not been characterized crystallographically, but have been shown to be monomers in solution. [HB(pz),]YCI(Hpz) has been characterized in the solid state and shown to have distorted-square-antiprismatic geometry.2b Finally, { [ H B ( ~ Z ) ~ ] ~ M ( P L - O ~ C C H ~ ) ) ~ complexes have been shown to be dimeric in solution and are presumed to be structurally similar to ([HB(pz)3]2Sm(cl-02CPh)!z, shown to have an acetate-bridged dimeric structure in the solid state and to also be dimeric in solution. Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for partial support of this research. The N S F (Grant CHE841 1172) and the N I H (Grant RR-02425) have supplied funds t o support NMR equipment, a n d t h e NIH ( G r a n t RR-02849) has supplied funds to support mass spectrometry equipment. We thank Professor William R. Gilkerson (University of South Carolina) for assistance and Professor 0. T. Beachley, Jr. (University of Buffalo), for helpful advice on the molecular weight studies. Supplementary Material Available: Table SI, listing crystallographic data, and Tables S I - S V , listing complete bond distances, bond angles, thermal parameters, and positional parameters of H atoms (12 pages); tables of observed and calculated structure factors (21 pages). Ordering information is given on any current masthead page.
